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PubMed1997

Electrical permeabilization of rat luteal cells: in situ phosphorylation of endogenous protein.

Progesterone synthesis in the corpus luteum is regulated primarily by luteinizing hormone which acts via the adenylate cyclase/cyclic AMP/protein kinase A signalling cascade. Protein phosphorylation therefore plays a key role in the regulation of steroidogenesis, but there are relatively few studies of the in situ phosphorylation of luteal cell substrates. This may in part reflect the difficulties inherent in measuring changes in protein phosphorylation in intact cells preloaded with 32P and difficulties in interpreting data obtained using broken cell preparations. We have now applied a method of stable permeabilization of luteal cell plasma membranes by exposure of cell populations to a high intensity electric field. Under optimum conditions (5 kV/cm, six discharges) electrical permeabilization reproducibly produced populations of luteal cells in which 70-80% of the cells were permeabilized, as assessed by Trypan blue exclusion and [14C] sucrose space measurements. Pores were stable for at least 1 h, and there were no ultrastructural changes to the cells that could be detected by transmission electron microscopy. Permeabilized cells showed rapid cyclic AMP-induced changes in phosphorylation of endogenous proteins when provided with [gamma - 32 P] ATP. Our results demonstrate that the electricity permeabilized luteal cell offers a useful model for studying intracellular events in steroidogenic stimulus-response coupling cascades.

Animals↗
PubMed1991

Biting periodicity index of Culex quinquefasciatus & its relationship with microfilaria periodicity in Pondicherry.

The biting periodicity index of the bancroftian filariasis vector, C. quinquefasciatus, was calculated on the basis of a large longitudinal data base and compared with the periodicity index of microfilariae of Wuchereria bancrofti. The biting periodicity index of the vector population was 29.78 and found to be close to the periodicity index of the microfilariae. The peak biting activity of the vector and peak appearance of microfilariae in the peripheral blood occurred at about 01.00 h, which accounts for the optimum infection of the vector population. The early night biting density of the vector population showed a highly significant (P less than 0.0005) linear relationship with all night biting density.

Animals↗
PubMed1976

Effect of drinking waters of high fluorine content on the urinary fluoride level.

The urinary fluoride level has been studied in 307 subjects consuming drinking waters of different fluoride concentrations. The urinary fluoride level was found to increase with the fluoride content of the drinking water. The urinary F level of the population group drinking water of optimum fluoride concentration was 1.14 mg of fluoride per litre. Thus, in regions where the drinking water contains an insufficient amount of fluoride, the fluoride content of domestic salt must be adjusted so as to ensure an about 1.14 mg/litre urinary F level of the population.

Adolescent↗
PubMed2005

Microbial population dynamics at effluent treatment plants.

The requirements for treated wastewater are becoming increasingly more stringent, and therefore the improved efficiency of biological treatment processes is indispensable at industrial effluent treatment plants (ETPs). Microorganisms such as bacteria play an important role in the natural cycling of materials and particularly in the decomposition of organic wastes. The knowledge of the interactions among these microbial populations needs to be harnessed for optimum evaluation and functioning of effluent treatment plants. Modern molecular techniques have revolutionized the methods of assessing these microbial populations. The combination of the results of these microbial assessments along with the on-site parameters at ETPs would favor an efficient treatment. In this review, the various approaches and importance of correlating the microbial population dynamics and treatment of wastewater at industrial ETPs has been elaborated.

Bacteria↗
PubMed1978

Effect of temperature on blue-green algae (cyanobacteria) in lake mendota.

The temperature optimum for photosynthesis of natural populations of blue-green algae (cyanobacteria) from Lake Mendota was determined during the period of June to November 1976. In the spring, when temperatures ranged from 0 to 20 degrees C, there were insignificant amounts of blue-green algae in the lake (less than 1% of the biomass). During the summer and fall, when the dominant phytoplankton was blue-green algae, the optimum temperature for photosynthesis was usually between 20 and 30 degrees C, whereas the environmental temperatures during this period ranged from 24 degrees C in August to 12 degrees C in November. In general, the optimum temperature for photosynthesis was higher than the environmental temperature. More importantly, significant photosynthesis also occurred at low temperature in these samples, which suggests that the low temperature alone is not responsible for the absence of blue-green algae in Lake Mendota during the spring. Temperature optima for growth and photosynthesis of laboratory cultures of the three dominant blue-green algae in Lake Mendota were determined. The responses of the two parameters to changes in temperature were similar; thus, photosynthesis appears to be a valid index of growth. However, there was little photosynthesis by laboratory cultures at low temperatures, in contrast to the natural samples. Evidence for an interaction between temperature and low light intensities in their effect on photosynthesis of natural samples is presented.

Journal Article↗
PubMed2006

Global and regional mortality from ischaemic heart disease and stroke attributable to higher-than-optimum blood glucose concentration: comparative risk assessment.

BACKGROUND: Cardiovascular mortality risk increases continuously with blood glucose, from concentrations well below conventional thresholds used to define diabetes. We aimed to quantify population-level effects of all higher-than-optimum concentrations of blood glucose on mortality from ischaemic heart disease and stroke worldwide. METHODS: We used population distribution of fasting plasma glucose to measure exposure to higher-than-optimum blood glucose. We collated exposure data in 52 countries from individual-level records in population health surveys, systematic reviews, and data provided by investigators. Relative risks for ischaemic heart disease and stroke mortality were from a meta-analysis of more than 200,000 participants in the Asia-Pacific region, with adjustment for other cardiovascular risk factors. RESULTS: In addition to 959,000 deaths directly assigned to diabetes, 1 490,000 deaths from ischaemic heart disease and 709,000 from stroke were attributable to high blood glucose, accounting for 21% and 13% of all deaths from these conditions. 1.8 million of these 2.2 million cardiovascular deaths (84%) were in low-and-middle-income countries (1,224,000 for ischaemic heart disease, 623,000 for stroke). 792,000 (53%) of deaths from ischaemic heart disease and 345,000 (49%) from stroke that were attributable to high blood glucose were in men. Largest numbers of deaths attributable to this risk factor from ischaemic heart disease were in low-and-middle-income countries of South Asia (548,000) and Europe and Central Asia (313,000), and from stroke in South Asia (215,000) and East Asia and Pacific (190,000). INTERPRETATION: Higher-than-optimum blood glucose is a leading cause of cardiovascular mortality in most world regions. Programmes for cardiovascular risk and diabetes management and control at the population level need to be more closely integrated.

Adult↗
PubMed2006

HAPLOFREQ--estimating haplotype frequencies efficiently.

A commonly used tool in disease association studies is the search for discrepancies between the haplotype distribution in the case and control populations. In order to find this discrepancy, the haplotypes frequency in each of the populations is estimated from the genotypes. We present a new method HAPLOFREQ to estimate haplotype frequencies over a short genomic region given the genotypes or haplotypes with missing data or sequencing errors. Our approach incorporates a maximum likelihood model based on a simple random generative model which assumes that the genotypes are independently sampled from the population. We first show that if the phased haplotypes are given, possibly with missing data, we can estimate the frequency of the haplotypes in the population by finding the global optimum of the likelihood function in polynomial time. If the haplotypes are not phased, finding the maximum value of the likelihood function is NP-hard. In this case, we define an alternative likelihood function which can be thought of as a relaxed likelihood function. We show that the maximum relaxed likelihood can be found in polynomial time and that the optimal solution of the relaxed likelihood approaches asymptotically to the haplotype frequencies in the population. In contrast to previous approaches, our algorithms are guaranteed to converge in polynomial time to a global maximum of the different likelihood functions. We compared the performance of our algorithm to the widely used program PHASE, and we found that our estimates are at least 10% more accurate than PHASE and about ten times faster than PHASE. Our techniques involve new algorithms in convex optimization. These algorithms may be of independent interest. Particularly, they may be helpful in other maximum likelihood problems arising from survey sampling.

Algorithms↗
PubMed2000

The genotypic landscape during in vitro evolution of a catalytic RNA: implications for phenotypic buffering.

The Tetrahymena group I ribozyme catalyzes the cleavage of a phosphodiester linkage in specific sequences of RNA. This phenotype can be used in an in vitro selection-amplification process to evolve variants that are capable of RNA catalysis in the presence of Ca(2+) as the sole available cation. With sufficient genotypic characterization of the population as it evolves, we have a rare opportunity of observing how the information stored in an evolving population responds to selective pressures, such as the requisite of catalyzing RNA cleavage in the absence of Mg(2+) or Mn(2+). In the present work, we examine the population dynamics of this system using sequence information from previous experimental work. We focus on two issues: How does the information content of the population evolve? and Is the system evolving as an adaptive walk on a rugged landscape? To investigate these questions, information theoretical parameters are examined. The evolution of the population is visualized by mapping the genotypic frequency distribution onto a two-dimensional projection of sequence space. The projection was generated using Hamming distances from the wild-type, starting sequence and a catalytically successful, evolved sequence. The evolution of the information content of the system was measured by calculating the grammar complexity of the observed sequences, which showed a very slight increase over 12 generations. This result is consistent with the system performing a search for a local optimum. The dynamics of the population in this sequence space is consistent with an adaptive walk on an uncorrelated, or "rugged," genotypic landscape, despite the observation that the phenotypic progress of the population appears smooth. The relative insensitivity of the phenotypic landscape to the variegation of the genotypic landscape suggests that the former is buffered against variation in the latter through various epigenetic-like mechanisms.

Evolution, Molecular↗
PubMed1983

Grazing, growth, and ammonium excretion rates of a heterotrophic microflagellate fed with four species of bacteria.

We studied aspects of the population growth of a microflagellate, Monas sp., isolated from Lake Kinneret, Israel. The protozoan growth rates, rates of ingestion of bacteria, and final population yields generally increased with increasing bacterial concentrations, although the exact relationship varied depending on the species of bacteria used as food. Grazing rates decreased hyperbolically with increasing food density. Gross growth efficiencies and ammonia excretion rates were similar over a range of food densities among the four species of bacteria. Population doubling times and ammonia excretion rates were lowest, and growth efficiencies were highest, at temperatures between 18 and 24 degrees C. Under optimum conditions, the microflagellates had average population doubling times of 5.0 to 7.8 h, average growth efficiencies of 23.7 to 48.7%, and average ammonia excretion rates of 0.76 to 1.23 mumol of NH(4) per mg (dry wt) per h.

Journal Article↗
PubMed1974

ZPG goals.

1. Zero Population Growth (ZPG) believes that the present population of the U.S. exceeds the optimum level for the continued well-being of its citizens. ZPG therefore advocates the achievement, by voluntary means, of an end to U.S. population growth by 1990, and a reduction in U.S. population size thereafter. Among the conditions necessary to achieve this goal, ZPG stresses: freedom of access for every person to all means of voluntary birth control; a major research effort to develop safer and more effective means of birth control; complete equality of opportunity for all women and men; and removal of all legal and societal pronatalist pressures. The population size should stabilize at a substantially reduced level which will maximize diversity, freedom of choice, and the quality of life for all. 2. ZPG believes that land is a resource too important to human survival to be subjected to misuse. Ecological land use planning is essential in determining the appropriate patterns of distribution of people on the land, and of migration between states and regions. Thoughtful land use planning at all levels of government is necessary to assure the long-range stewardship of the land and well-being of mankind. 3. ZPG believes that human activities are causing the rapid depletion of the world's available stock of mineral resources. Simultaneously those activities are resulting in increased pollution of land, air, and water resources. ZPG therefore recommends 1) reduction in the rate of growth and eventual stabilization of U.S. consumption of nonrenewable resources; and 2) rapid stabilization of total national energy consumption at least until environmentally sound sources are developed. ZPG recognizes that none of its goals can be justified unless concurrently with their achievement adequate levels of income, health care, and educational opportunity are assured to all persons.

Americas↗
PubMed2002

The effect of polymer addition on granulation in an anaerobic baffled reactor (ABR). Part II: compartmentalization of bacterial populations.

The microbial ecology of wastewater treatment plants remains one of the least understood aspects in both aerobic and anaerobic systems, despite the fact that both processes are ultimately dependent on an active biomass for operational efficiency. Ultimately, future developments in anaerobic treatment processes will require a much greater understanding of the fundamental relationships between bacterial populations within the biomass if optimum process efficiency is to be fully realised. This study assesses the influence of polymer addition on granule formation within an ABR and compares the ecology of the biomass in each compartment of two ABRs treating ice-cream wastewater. To our knowledge, this is the first reported characterisation of the microbiology of acidogenic and methanogenic bacteria in the individual compartments of an ABR. The polymer-amended reactor contained sludge that had a greater density of anaerobic bacteria and larger and denser granules than the control reactor, indicating that polymer addition possibly contributed to the retention of active biomass within the ABR. The average fraction of autofluorescent methanogens was lower, with 1.5% being in the initial compartments of the ABRs, compared to the last compartment which had 15%, showing that each compartment of an ABR had a unique microbial composition. Partial spatial separation of anaerobic bacteria appeared to have taken place with acidogenic bacteria predominating in the initial compartments and methanogenic bacteria predominating in the final compartments. Scanning electron micrographs have revealed that the dominant bacteria in the initial compartments of the ABR (Compartments 1 and 2) were those which could consume H2/CO2 and formate as substrate, i.e. Methanobrevibacter, Methanococcus, with populations shifting to acetate utilisers, i.e. Methanosaeta, Methanosarcina, in the final compartments (Compartments 3 and 4). In addition, there appeared to be a stratified structure to the bacterial genera present within the granules.

Bacteria, Anaerobic↗
PubMed2002

Parents' experiences of midwife-managed care following the loss of a baby in a previous pregnancy.

AIMS OF THE STUDY: This article reports on research that explored the impact of the Special Delivery Service, a midwife-managed intervention, developed as an addition to routine care to support and educate high-risk pregnant women and their partners subsequent to the death of a baby in a previous pregnancy. BACKGROUND: Approximately 40,000 families suffer the trauma of a neonatal death* annually in the USA, while statistics for Canada and Australia give similar numbers relative to population. Since many more babies die than those accounted for in these statistics, through stillbirth, miscarriage and Sudden Infant Death Syndrome, more than the above-cited 2% of childbearing couples will face the trauma of the loss of a baby. RATIONALE: The resultant threat that this situation may pose to the health of the mother has been extensively documented in the literature. However, despite the recent growth in knowledge about the impact of perinatal loss and bereavement, few interventions are specifically designed to support Australian and Canadian women and their partners during a pregnancy following the loss of a baby. METHODOLOGY: This phenomenological study explored women's and their partners' experiences of grief and loss and the support offered to them through the Special Delivery Service programme. RESULTS & DISCUSSION: In the face of funding and organizational changes to both the Australian and Canadian health care systems that have eliminated or reduced some services, this research reinforced the need for individualized, compassionate midwifery care and the urgent need for genuinely empathic and supportive health care services for these women and their partners. It also emphasized the need for couples to be informed and supported so that gender differences in grieving do not become a divisive element in the relationship. CONCLUSIONS: The findings have implications for both nurses and midwives in their practice in countries where optimum care of this vulnerable population is not routinely available. The research supports midwife-managed models of care to ensure women and their families are appropriately supported in crisis. The findings provide insight also into the diverse grief response among couples and the difficulties experienced in a pregnancy following the loss of a baby.

Attitude to Death↗
PubMedDate not supplied

[Years of potential life lost in Mexico. Applications in the planning of health services].

During health care services planning, rational and coherent information is required in order to allocate resources in accordance with local relative need. In an attempt to recognize the national condition, Stone's method was used. This is a semi-quantitative method for analysing the relationship between health care resources and need. Years of potential life lost index was used for need assessment among the states, and confronted to its Federal Public Health Investment. The optimum resource/need ratio is regarded as that pertaining to the reference population, the nation as a whole. Deviation from the optimum ratio in the states is interpreted as a manifestation of inequitable resource distribution. The results show striking differences in needs and resources. Resource/need ratio varied from 0.21 in Oaxaca to 3.79 in Distrito Federal. The states least favoured in resource sharing were Oaxaca, Puebla, Hidalgo and México. On the other hand, Tamaulipas, Baja California Sur, Quintana Roo and Distrito Federal exceeded the optimum. These indexes permit a quantitative expression of the relationship between need and resources in order to reach geographical equity.

Financing, Government↗
PubMedDate not supplied

[A dynamic study of the count of a commercial muskrat population (Ondatra zibethica: Mammalia) in a simulation model].

Density-dependent mechanisms of muskrat numbers regulation in Karakalpakstan were investigated by mathematical imitation model. The behaviour of model and native population is quite similar. The upper limit for optimum level of density under given conditions is determined by exogenous factors. Within population mechanisms lead the density and population structure to the level suitable for given conditions.

Animals↗
PubMed1971

pH as a determinant of cellular growth and contact inhibition.

1) Both the growth rate and the maximum population density of several normal, virus-transformed, and cancer cells were markedly pH-dependent; the optimum varied from pH 6.9 to 7.8. At the optimum pH, some diploid human cells attained population densities comparable to those of cancer or virus-transformed cells. Contact inhibition of growth is facilitated by repeated fluctuations of pH in nonphysiological ranges, and may not be an intrinsic and necessary attribute of diploid cells in culture. 2) At pH 8.3, at which there was little or no cellular multiplication, the protein content per cell increased 2- to 5-fold over a period of 10-16 days, and was slowly reversed to normal concentrations on restoration of pH to the optimal range. 3) Uridine uptake by contact-inhibited human cell cultures was stimulated by refeeding with salt solution, and to the same extent as by complete (serum-supplemented) growth medium; that immediate increase did not involve the reinitiation of cellular growth and multiplication. Contact inhibition was, however, reversed in 2-4 days by an appropriate increase in the serum concentration of the medium.

Adenoviridae↗
PubMed2005

An intervention study to increase knowledge and use of folic acid among relatives in neural tube defect-affected families in Washington, D.C.

BACKGROUND: Little is known about the level of knowledge and use of folic acid among near relatives in U.S. families of a child with spina bifida. We hypothesized that relatives would be more knowledgeable than the general population and more likely to take folic acid. Further, we hypothesized that relatives would be more motivated by an intervention to increase their use of folic acid. METHODS: We conducted an intervention study among females in families attending a hospital spina bifida clinic in Washington, DC. RESULTS: The 231 subjects consisted of the affected individuals, mothers, sisters, and aunts. The average age was 34 years. At baseline, most (87.4%) reported that they had heard of folic acid; 37.6% were currently taking multivitamins with folic acid and 6.9% were taking folic acid tablets. The intervention significantly increased both knowledge (to 99%) and intake of folic acid from 41.9 to 48.5%. Folic acid intake increased significantly among African-American women and women with less education, women who were older, married, with children, and nonsmokers. CONCLUSIONS: This intervention was successful in increasing folic acid intake among female relatives in spina bifida-affected families. By the end of the study, almost all women had heard of folic acid and folic acid use had increased by 16%. Among these women at higher than expected risk for having an affected child, this rate of intake, while more than the general population, still falls short of optimum. Fortification of food with folic acid may be the only way to ensure increased folic acid intake.

Adolescent↗
PubMed2001

Interaction of Nosema pyrausta and temperature on Ostrinia nubilalis egg production and hatch.

Nosema pyrausta is an obligate pathogen causing reduced fecundity and longevity of Ostrinia nubilalis. This study was conducted to determine the combined effects of N. pyrausta infection and temperature on O. nubilalis egg production and hatch. N. pyrausta-infected and noninfected O. nubilalis were maintained in two different temperature regimes. The first regime allowed females to oviposit under optimum conditions (27 degrees C, 65% RH, 16:8 (L:D)), while females in the second regime were held initially under the same humidity and light conditions, but a constant temperature of 16 degrees C for 1 week after which they were transferred to optimum ovipositional conditions. Studies were performed initially with O. nubilalis populations and later with individual mating pairs. In studies with O. nubilalis populations, the mean number of eggs laid per female under optimum conditions was 660, while N. pyrausta-infected females held initially at 16 degrees C laid 116 eggs per female. In studies with individual mating pairs, N. pyrausta infection reduced egg production per female 53 and 11% in the 16 and 27 degrees C temperature regimes, respectively, compared to noninfected females under optimum conditions. Exposure to 16 degrees C temperatures early in the ovipositional period had a more profound impact on reducing egg production in N. pyrausta-infected than noninfected O. nubilalis.

Animals↗
PubMed1994

Mutation load and mutation-selection-balance in quantitative genetic traits.

Haldane (1937) showed that the reduction of equilibrium mean fitness in an infinite population due to recurrent deleterious mutations depends only on the mutation rate but not on the harmfulness of mutants. His analysis, as well as more recent ones (cf. Crow 1970), ignored back mutation. The purpose of the present paper is to extend these results to arbitrary mutation patterns among alleles and to quantitative genetic traits. We derive first-order approximations for the equilibrium mean fitness (and the mutation load) and determine the order of the error term. For a metric trait under mutation-stabilizing-selection balance our result differs qualitatively from that of Crow and Kimura (1964), whose analysis is based on a Gaussian assumption. Our general approach also yields a mathematical proof that the variance under the usual mutation-stabilizing-selection model is, to first order, micro/s (the house-of cards approximation) as micro/s tends to zero. This holds for arbitrary mutant distributions and does not require that the population mean coincide with the optimum. We show how the mutant distribution determines the order of the error term, and thus the accuracy of the house-of-cards approximation. Upper and lower bounds to the equilibrium variance are derived that deviate only to second order as micro/s tends to zero. The multilocus case is treated under the assumption of global linkage equilibrium.

Alleles↗